Ion beam etching is a method of removing small (e.g., nanometer scale) amounts of material from a substrate such as a wafer. Often, a patterned mask such as a photoresist or a hard mask is applied to a surface, and then ion beam etching is used to remove the unmasked material, leaving the masked material.
In ion beam etching, the wafer, or other substrate being etched, can be rotated around a central axis during the etching process so that the angled ion beam has access to all sides of the feature being etched.
One of the major challenges facing semiconductor photolithography involves obtaining high density features, because typical printing processes for applying the mask cannot easily apply a pattern having a small spacing, less than about e.g., 28 nm, between adjacent features. Various alternate methods to obtain a spacing less than 28 nm between features have been attempted. For example, the mask can be applied in multiple, offset printing steps, to increase the density of features and thus decrease the spacing therebetween. As another example, an encapsulating coating or second mask can be applied over a first mask, after which the original mask is removed, thus creating two mask features for each first mask feature.
These methods can be difficult, complicated, and do not always provide acceptable features.